In-flight refueling (or air-to-air refueling) is an important method for extending the range of aircraft traveling long distances over areas having no feasible landing or refueling points. Although in-flight refueling is a relatively common operation, especially for military aircraft, precise positioning of a second aircraft (the receiver aircraft, for example) with respect to a first aircraft (the tanker aircraft, for example) is required in order to provide a safe engagement of the first aircraft with the second aircraft for the dispensing of fuel. In-flight refueling operations often take place during low-light conditions, including operations at night and during inclement weather, such that it may be advantageous to illuminate the in-flight refueling operation by, for instance, providing lighting installed on the first aircraft to illuminate the second aircraft as it approaches the first aircraft for in-flight refueling. Such illumination may aid, for instance a refueling system operator onboard the first aircraft, in visualizing the second aircraft as it approaches for an in-flight refueling operation.
There are currently two primary systems for in-flight refueling. One system is the boom refueling system. The boom refueling system typically comprises a rigid boom extended from a refueling aircraft. At one end of the boom is a refueling nozzle and adjacent the refueling nozzle are airfoils, which are controlled by a refueling system operator such as, for instance, a boom operator, on the refueling aircraft. The airfoils provide maneuverability of the boom with respect to an aircraft that is to be refueled. For the aircraft that is to be refueled, the second aircraft, the operator of the second aircraft must maneuver the second aircraft to within an in-flight refueling position, below and aft of the first aircraft. Upon maneuvering into the in-flight refueling position, the boom operator controls the airfoils to position and mate the boom into a refueling connection on the second aircraft.
Another type of refueling system is the probe and drogue system. In the probe and drogue system, a refueling hose having a drogue disposed on one end is trailed behind first aircraft (the tanker aircraft). The second aircraft has a probe that is flown by its operator into the drogue. As the drogue typically moves away from the second aircraft as it approaches, great skill and maneuvering ability is required by the operator of the second aircraft to mate the probe with the drogue. It is preferable, in the probe and drogue system, for the second aircraft to approach and enter the in-flight refueling position relative to the first aircraft as in the boom system, except in this case, the operator of the second aircraft is also responsible for “flying” the second aircraft's probe directly into the trailing drogue, because the drogue lacks the control surfaces that are provided on the refueling boom. The refueling system operator may be responsible, however, for extending the drogue to a trailing position that is within a suitable range of the second aircraft, such that the operator of the second aircraft may safely mate the probe with the drogue.
For both types of in-flight refueling systems, the refueling system operator of the first aircraft may, in some cases (such as in remote airborne refueling operator (RARO) systems), be positioned remotely from the refueling equipment (including boom equipment and drogue equipment) such that the refueling system operator may view the in-flight refueling operation remotely via, for instance, a camera positioned to capture an image of the in-flight refueling operation and direct the image to a display that may be visible to the refueling system operator. In such RARO systems, for in-flight refueling operations often take place during low-light conditions, including operations at night and during inclement weather, it may be advantageous to illuminate the in-flight refueling operation by, for instance, providing lighting installed on the first aircraft to illuminate the second aircraft as it approaches the first aircraft for in-flight refueling such that the RARO camera may be capable of capturing images of the in-flight refueling operation.
Illuminating systems have been disclosed for illuminating in-flight refueling operations, including those involving a RARO system such that the refueling system operator may remotely view the in-flight refueling operation. However, in the disclosed illuminating systems, the lighting units used are tungsten filament lamps that produce emissions including large amounts of light in the visible wavelengths such that the illuminating system may hamper the vision of an operator of the second aircraft as it approaches the first aircraft for an in-flight refueling operation. Also, the visible light emissions produced by the tungsten filament lamps are not covert, and may be visible to hostile observers and/or aircraft. In addition, the tungsten filament lamps also have a relatively short useful life of only 200-300 hours and a large electrical power requirement. The tungsten filament lamps also produce a large amount of heat and may require diffusing and filtered optics that result may result in the lamps' emissions having a non-uniform illumination field.
Therefore, there exists a need for an illuminating system that provides eye-safe and covert illumination that is adapted to uniformly illuminate, for instance, an area to rear and aft of a first aircraft that may contain an in-flight refueling position. There also exists a need for an illumination system and device that produces eye-safe, covert emissions to provide illumination to an in-flight refueling position but that does not require a large electrical power supply or generate a large amount of excess heat. There also exists a need for an illuminating system that comprises component parts that are reliable, durable, and suitable for carriage by a first aircraft configured to conduct in-flight refueling operations.